A surveillance camera placed outdoor is required to work outdoor over a long period of time, and is thus inevitably exposed to rain. For an existing surveillance camera, its housing for accommodating a substrate and other internal components includes a base 1 and an upper cover as shown in FIG. 1, the base 1 is provided with a retaining ring 11 at the periphery of its bottom and a plurality of bolt holes 12 for bolts to go through on its periphery in the circumferential direction, the base 1 is fixed firmly to the upper cover by bolts to form a cavity; a mounting hole 13 is provided on the bottom of the base 1 for installing a dehumidifying means. For facilitating installation and removal, the bolt hole 12 in the base 1 goes throughout the base 1 from top to bottom; When the surveillance camera is under installation, the bolt is made to go throughout the bolt hole 12 from the bottom of the base 1 and connected with the upper cover.
With a surveillance camera of this structure in operation, since the bottom face of the base 1 faces upward, rainwater will accumulate at the bottom of the base 1; when water reaches a certain amount, it may flow from the bottom end of the bolt hole 12 (the bottom end of the bolt hole 12 faces upward while being used) into the housing of the surveillance camera along the bolt hole 12, thus causing fog, dew, etc. inside the surveillance camera, furthermore this may even cause corrosion of the internal substrate in severe cases, which eventually causes the surveillance camera to lose monitoring function.
Besides, when there is fog and dew inside the surveillance camera, the normal use of the dehumidifying means will also be affected.